Numerous sensors that acquire at least one rotation characteristic of rotatable, especially rotating, objects are believed to be understood from the related art. In principle, rotation characteristics are characteristics that at least partially describe the rotation of the rotatable object. For example, these may be angular velocities, rotational speeds, angular accelerations, angles of rotation, angular positions or other characteristics that can characterize a continuous or discontinuous, even or uneven rotation of the rotatable object.
Examples of such sensors are discussed in Konrad Reif (publisher): Sensoren im Kraftfahrzeug [Sensors in the Motor Vehicle], 1st edition 2010, pages 63-73. A particular focus of the present invention, although not restricted thereto in principle, is a rotational speed acquisition, especially the rotational speed acquisition of charge devices, in particular in exhaust-gas turbochargers. This rotational speed acquisition may specifically be set up to acquire a rotational speed of a rotor of the exhaust-gas turbocharger. This rotor is typically provided with a plurality of compressor blades and may therefore also be referred to as a compressor wheel.
A device for rotational speed acquisition for a charge device, especially a rotor of an exhaust-gas turbocharger, is discussed in publication DE 10 2007 005 769 A1. Here, permanent magnets and a sensor circuit are employed separately, which are placed in physically different locations. A housing is used, which includes the rotor and is manufactured from a plastic material, in which the permanent magnets are embedded as insertion parts. The sensor circuit is accommodated in a recess on an outer side of the wall of the housing.
Other devices known from the related art typically use a cylindrical sensor, which has the smallest possible diameter and is introduced into a bore of the housing from the outside. Since the high temperatures in the vicinity of the compressor wheel usually exclude the use of conventional semiconductor components, a thermal decoupling of the sensor housing from the housing of the compressor wheel would be desirable.
Despite the numerous advantages of the previously known rotational speed acquisition devices, there is consequently still room for improvement.